Climate Change and the Hydrology and Morphology of Freshwater Ecosystems - Climate Change Impacts on Freshwater Ecosystems - page 72

Figure 4.3 Habitats in the river Lambourn, southern England.
relatively stable habitats where they are sheltered from shear stress. Many may lack
adaptations and be washed downstream (Blanch et al . 2000; Imbert et al . 2005).
When disturbances become highly unpredictable, species might display risk-
spreading strategies, for example, asynchronous hatching of eggs (Lytle & Poff
2004). Behavioural adaptations enable organisms to respond directly to individual
floods and droughts and unstable substrates by moving to refuges, following use of
cues that they can detect (Lytle & Poff 2004). Droughts and low flows elicit other
strategies. There may be physiological resistance (Smith & Pearson 1985), adapted
life cycles, allowing early maturation and flight of adults, or resting stages (Ladle &
Bass 1981; Williams 1987; Bunn 1988). There may also be increased mobility with
organisms seeking out remaining higher-flow habitats (Harrison 1966; Olsson &
Söderström 1978; Delucchi 1989). Climate change may also result in death through
sediment injury or burial, increased drift downstream, physiological problems for
respiration, as particles settle on gill filaments, and through low oxygen concent-
rations in the water due to the deposition of fine organic sediments (Stazner &
Holm 1982; Strommer & Smock 1989; Hart & Finelli 1999; Holomuzki & Biggs
2003; Gordon et al . 2004). There may also be food shortages as food sources
(organic matter, periphyton) are buried by settling particles or scoured by the
current. There can be an increase of the sediment concentration in suspension in
the water column (affecting filter feeders positively) or a decrease in potential prey
(loss of individuals due to drift, burial) for predators.